As a gas circuit breaker applied to a high-voltage electric power system, employed is a puffer type gas circuit breaker which performs extinguishment by blasting a quenching gas to an arc in association with a contact opening operation in an interruption part. When a short-circuit fault occurs in the electric power system and a short-circuit current flows, a trip signal is sent to this conventional puffer type gas circuit breaker. The puffer type gas circuit breaker receives the signal, then moves a movable main contact away from a fixed main contact forming a main current path with an operator using oil pressure or energy stored in a spring. Then the puffer type gas circuit breaker moves a movable arc contact from a fixed arc contact at a high speed, and at the same time, drives a puffer cylinder connected with an insulating rod so as to compress a quenching gas in a compression chamber formed with the insulating rod and a piston. Thereafter, the gas circuit breaker blasts the high-pressure quenching gas through an insulating nozzle to an arc ignited between the arc contacts, thereby interrupts the short-circuit current at an arc current zero point.
This puffer type gas circuit breaker obtains a stable high blast pressure. However, as the quenching gas heat-expanded by the heat of arc ignited between the arc contacts acts as a counterforce to the puffer cylinder to compress the quenching gas in the compression chamber, an operator having high operation energy is required to overwhelm the counterforce to ensure desired interruption performance. On the other hand, a puffer type gas circuit breaker applying heat of arc generated upon contact opening to a blast pressure is known. This puffer type gas circuit breaker is provided with a floating piston placed in a compression chamber via a spring, so as to control an extreme pressure rise due to the heat of arc by the operation of the floating piston (for example, see Patent Document 1).
[Patent Document 1] Japanese Patent Laid-Open No. S63(1988)-88724
However, in the above conventional puffer type gas circuit breaker, as the floating piston is placed in the compression chamber via the spring, the extreme pressure rise due to the heat of arc can be suppressed, but the operation characteristic of the floating piston based on the gas pressure is unstable. Accordingly, in this arrangement, stable blasting cannot be maintained, and stable interruption performance cannot be obtained without difficulty. For this reason, in a circuit breaker used in a high-voltage electric power system, to maintain a stable and high blast pressure upon quenching gas blasting as in the case of the general puffer type gas circuit breaker, it is necessary to form a compression chamber with a puffer cylinder and a piston so as to mechanically compress the quenching gas in the compression chamber in association with an interruption operation. Accordingly, as described above, an operator with high operation energy is required to perform an interruption operation while overwhelming the pressure rise in the compression chamber related to the interruption operation and the pressure rise in the compression chamber due to the heat of arc.
The present invention has been made in consideration of the above situation, and provides a current interruption method for a puffer-type gas circuit breaker for enabling downsizing of an operator and reduction of operation force, and for maintaining a stable and high blast pressure, and a puffer type gas circuit breaker employed in the method.